An implicit enthalpy scheme for one-phase Stefan problems

A compact finite-difference scheme to solve one-phase Stefan problems in one dimension is described. Numerical experiments indicate that the moving interface is obtained withO(t) accuracy when 3–4 iterations per time step are used to solve the nonlinear implicit scheme. The scheme can be adapted to ADI methods in higher dimensions.     

云计算安全需求分析研究

云计算是当下发展迅速的信息技术之一。由于其外包式的服务方式,云计算中的安全问题受到人们格外关注。只有妥善地保障云计算的安全,才不会掣肘云计算的发展和推广。鉴于云计算的复杂性和多面性,文章着眼云计算有别于传统技术的新特点、新趋势,首先提出了考量云计算安全需求的多维视角,随后围绕云计算具体实施过程中的若干关键技术,对云计算中的安全需求进行了细致全面的分析和阐释。     

Measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V) by a microsecond-resolution transient technique

A microsecond-resolution pulse heating technique was used for the measurement of the heat of fusion of titanium and a titanium alloy (90Ti-6Al-4V). The method is based on rapid (50- to 100-s) resistive self-heating of the specimen by a high-current pulse from a capacitor discharge system and measuring, as functions of time, current through the specimen, voltage across the specimen, and radiance of the specimen. Melting of the specimen is manifested by a plateau in the measured radiance. The time integral of the net power absorbed by the specimen during melting yields the heat of fusion. The values obtained for heat of fusion were 272 J · g^–1 (13.0 kJ · mol^–1) for titanium and 286 J · g^–1 for the alloy 90Ti-6Al-4V, with an estimated maximum uncertainty of ±6% in each value.Paper presented at the Second Workshop on Subsecond Thermophysics, September 20–21, 1990, Torino, Italy.     

Web服务器安全威胁与防范技巧

WEB服务器主要是面向互联网的,随着人们对互联网服务的需求不断扩大,各种互联网应用服务日益增多,Web服务器便成为众多信息化应用中最容易遭受攻击的对象。文章中主要介绍了几种常见的Web服务器安全威胁,并提出了相应的安全防范技巧。     

类金刚石膜的制备及其影响因素

概述了近年来制类金刚石膜的新技术如双射频辉光放电（RF－RF）法，射频－直流辉光放电（RF－DC）法和微波－射频（MW－RF）法等，并且对影响类金刚石膜制备及性能的因素如基体材料，制备类金刚石膜时在膜中添加元素，类金刚石膜与基材之间的中间层等进行了较全面的分析。     

钢结硬质合金材料的研究进展

介绍了钢结硬质合金的性能特点及制备工艺,简述了近年来在钢结硬质合金领域开展的研究与取得的进展,对钢结硬质合金的应用进行了分类归纳,展望了其发展前景。     

Advanced experimental and numerical methods for the analysis of the dynamic forming press behavior

Numerical simulations are used to estimate the dynamic behavior of new concepts of forming presses as well as to improve the dynamic properties of existing machines. These simulations are to be parametrized with appropriate values in order to yield most accurate results. In many cases neither the way of building up the simulation model for the specific problem nor an appropriate method for gathering the needed date are given in advance. Regarding these facts this paper intends both to characterize the way of building up complex simulation models by using basic simulation modules and to describe methods for the identification of the needed parameters that work even under conditions that hitherto made parameter identifications impossible or at least very time-consuming. In this context recent developments in simulating press dynamics will also be characterized as new modal analysis methods that are not yet established in the field of forming technique. The research activities were financed by the European Research Association for Sheet Metal Working.     

表面技术用新型加热与干燥设备

夜面涂装加热与干燥设备是近年来开发的节电新技术,可较传统热风炉或一般远红外炉节电15～40%,炉内上下温差3～8℃。文章提出用系统优化的原理和方法对乳白石英管低温辐射加热进行研究,设计中采用辐射密度分布法和部份功率控制法。     

气液固三相床中合成甲醇与二甲醚

叙述了气液固三相催化反应技术的主要特点和应用领域，并着重介绍了三相床合成甲醇和二甲醚的试验研究内容和成果。     

我国化肥催化剂工业现状

全国48家化肥催化剂制造厂总能力为57Kt/a,产量近30kt/a,设备利用率不到50%。平均万吨氨耗催化剂10.36t,高于国外5.60t水平。现生产31个品种203个型号的催化剂中有103种经部级鉴定,但经常使用的约50种。目前化肥催化剂工业水平与国外相比还存在四方面差距。